This invention relates to a method of recovering heat from slag, from ore refining processes and to apparatus for practicing the method.
It is well known that the slag produced in an ore refining or smelting process as, for example, in a blast furnace, is of a great quantity and is at a high temperature, and the heat energy carried away by this slag is of tremendous quantity. However, this slag is ordinarily allowed to flow onto a melt dumping yard to cool naturally or by sprinkling with water, and, according to the present practice, there is no recovering whatsoever of this tremendous heat energy, which is therefore wasted.
As one example, the case of slag in a blast furnace will be considered quantitatively. It is said that the quantity of slag produced in a blast furnace is ordinarily of the order of 0.28 to 0.35 parts per one part of pig iron. From a blast furnace of 10,000-metric ton daily production, the slag output is approximately 3,000 metric tons per day. On the assumption that the slag temperature is 1,500.degree. C., and that the specific heat of the slag is 0.24 Kcal./kg..degree. C., that heat loss is approximately 1.08 .times. 10.sup.9 Kcal. per day, or 45.0 .times. 10.sup.6 Kcal. per hour. Converted into terms of fuel oil, this rate is 4,500 kg./hour, which is a considerable quantity.